Venting or exhausting combustion gases from fireplaces and, more recently, appliances having combustion chambers such as furnaces or water heaters typically is and has been accomplished by providing a vertically oriented chimney with a flue therein for convectively conducting hot combustion byproducts from the combustion chamber to the atmosphere.
In new construction, particularly in multi-unit buildings or townhouses, and in remodeling or adding new appliances to existing buildings, it is sometimes extremely difficult to provide the traditional vertically oriented chimney.
The result of the just stated problem was the development of venting systems for exhausting hot combustion gases horizontally as well as in the traditional vertical orientation. An example of this type of venting system is disclosed in U.S. Pat. No. 4,856,982.
With horizontal or through-wall venting systems typified by the system shown in U.S. Pat. No. 4,856,982, one problem is that heat tends to rise to the upper portion of the horizontal run and another problem is that the venting system frequently must penetrate a combustible wall. There have been attempts to address these problems. U.S. Pat. No. 4,765,308 suggests that a flue pipe may be provided with a number of sleeves having annuli therebetween whereby the flue pipe is isolated from the wall that it passes through. Additionally, convection is used to generate an air flow in and out of at least one of the spaces between the sleeves.
U.S. Pat. No. 4,765,308 also illustrates that through-wall or roof venting systems which enable or permit a flow of ambient air to enter the combustion chamber are well known. Convection has been used to generate flow of air or combustion gases in desired directions either into or out of a combustion chamber and to bring about a limited amount of cooling of the venting system. See U.S. Pat. Nos. 4,543,942, 4,750,433 and 4,757,802 disclosing other vent or insulated flue assemblies for through-wall, horizontal venting applications.
While the above cited patents represent improvements and advances for exhausting hot combustion gases horizontally through combustible materials, there are several problems which have remained unaddressed. First, there is the need to make absolutely sure that the hot exhaust gases are sufficiently cooled by the time they reach a combustible wall and that they are sufficiently cooled when exhausted or expelled from the exhaust system into the atmosphere. As long as hot combustion gas was being exhausted vertically, usually well above ground level, there was relatively little danger of burning people, pets or vegetation near the exhaust vent. When exhausting hot gases (initially at about 600 to 700 degrees Fahrenheit) at or near the ground, however, it is crucial that the temperature of the gas being blown out be reduced to a non-hazardous level. Moreover, the vent apparatus or hardware at the building exterior must itself be cool enough to avoid burning a person or a child who might inadvertently touch it.
Other problems with through-wall venting systems include the accumulation of soot and other combustion byproducts near or around the vent or discharge opening at the outside of the building, and the formation of condensation as a result of the too rapid cooling of combustion gases. Additionally, ambient atmospheric conditions, high winds or severe cold, can cause problems with existing through-wall power vent systems, high back pressure or exacerbated condensation problems are but two examples. Thus, there remains a need for a safe, efficient inexpensive power venting system that substantially reduces the temperature of combustion gases prior to their discharge into the atmosphere, minimizes problems with condensation, and avoids staining the building at or near the discharge site.